base64.c

uC/OS2系统下的base64源码。开发环境：ads1.2

#include "base64.h"
#include "config.h"

//#define isalnum(c) ( (c>='A' && c<='Z') || (c>='a' && c<='z') || (c>='0' && c<='9') )
#define is_base64(c) (isalnum(c) || (c == '+') || (c == '/'))


const char *base64_chars = 
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";


//对bytes_to_encode进行base64编码，并输出到outBuf中。
//注意：要获得完整的base64编码，outBuf的大小必须大于或等于原始数据的(1+1/3)倍
//		（如果原始数据大小不是3的倍数，outBuf应多增加4字节缓存）。
unsigned char *base64_encode(const unsigned char *bytes_to_encode, unsigned int in_len, 
				   unsigned char *outBuf, unsigned int bufSize) 
{
	int i = 0, j = 0;
	int outIdx = 0;
	unsigned char char_array_3[3], char_array_4[4];

	if ( bytes_to_encode == NULL || outBuf == NULL )
		return NULL;

	while (in_len--)
	{
		char_array_3[i++] = *(bytes_to_encode++);
		if (i == 3) 
		{
			char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
			char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
			char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
			char_array_4[3] = char_array_3[2] & 0x3f;

			for(i = 0; (i <4) ; i++)
			{
				if ( outIdx >= bufSize )
					return outBuf;
				outBuf[outIdx++] = base64_chars[char_array_4[i]];
			}
			i = 0;
		}
	}

	//处理不足3字节的数据（最后1字节或2字节）
	if (i)
	{
		//用0补足3字节原始数据
		for(j = i; j < 3; j++)
			char_array_3[j] = '\0';

		char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
		char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
		char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
		char_array_4[3] = char_array_3[2] & 0x3f;

		for (j = 0; (j < i + 1); j++)
		{
			if ( outIdx >= bufSize )
				return outBuf;
			outBuf[outIdx++] = base64_chars[char_array_4[j]];
		}

		//将输出的base64编码补足4的倍数。
		while((i++ < 3))
		{
			if ( outIdx >= bufSize )
				return outBuf;
			outBuf[outIdx++] = '=';
		}
	}

	return outBuf;
}



//对encoded_string中的base64编码进行解码，并输出到outBuf中。
//注意：要获得完整的解码数据，outBuf的大小必须大于base64编码数据的3/4。
unsigned char *base64_decode(const unsigned char *encoded_string, unsigned char *outBuf, unsigned int bufSize) 
{
	int in_len = strlen((const char *)encoded_string);
	int i = 0, j = 0, in_ = 0;
	int outIdx = 0;
	unsigned char char_array_4[4], char_array_3[3];

	if ( encoded_string == NULL || outBuf == NULL )
		return NULL;

	while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) 
	{
		char_array_4[i++] = encoded_string[in_]; in_++;
		if (i ==4) 
		{
			for (i = 0; i <4; i++)
				char_array_4[i] = strchr(base64_chars, char_array_4[i]) - base64_chars;

			char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
			char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
			char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

			for (i = 0; (i < 3); i++)
			{
				if ( outIdx >= bufSize )
					return outBuf;
				outBuf[outIdx++] = char_array_3[i];
			}
			i = 0;
		}
	}

	if (i) 
	{
		for (j = i; j <4; j++)
			char_array_4[j] = 0;

		for (j = 0; j <4; j++)
			char_array_4[j] = strchr(base64_chars, char_array_4[j]) - base64_chars;

		char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
		char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
		char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

		for (j = 0; (j < i - 1); j++) 
		{
			if ( outIdx >= bufSize )
				return outBuf;
			outBuf[outIdx++] += char_array_3[j];
		}
	}

	return outBuf;
}